| trip on(verb, expression, phrasal verb, meet, catch) |
| trip over(verb, expression, phrasal verb, establish, strike) |
| tumble |
| tumble into(expression, catch, notice, spot, discover) |
| tumble on |
| unbury |
| undergo(verb, meet, bear, face, suffer) |
| understand(verb, discover, find, surprise) |
| unfold(fix, resolve, crack, answer) |
| unlock(verb, fix, do, resolve, have) |
| unmask(verb, catch, observe, notice, crack) |
| unravel(resolve, crack, answer) |
| unriddle(verb, fix, do, resolve, have) |
| untangle(fix, resolve, crack, answer) |
| unwrap(verb, open, strike, crack, reveal) |
| uproot |
| wise up to(expression, idiom, catch, notice, spot) |
| work(fix, resolve, crack, answer) |
| work out(expression, resolve, crack, answer, manipulate) |
| zero in on(verb, expression, idiom, phrasal verb, establish) |